1. Field of the Invention
The present invention relates to a circuit arrangement for recognizing zero transition of signals, in which the signals are fed to a zero transition detector and to an amplitude evaluator, and more particularly to a circuit arrangement in which the zero transition detector produces rectangular signals which are assigned to the zero transitions of the signals, and in which the amplitude evaluator produces amplitude signals which, at least until the occurrence of the particular next zero transition, indicate that prior to this zero transition the amplitude of the signal was greater than a predetermined threshold voltage.
2. Description of the Prior Art
When data are transmitted from a data transmitter to a data receiver, it is frequently necessary for the zero transitions of signals representing the data to be established as accurately as possible. For example, in the case of the read-out of digital data stored on magnetic discs, it is necessary to precisely determine the zero transitions of different read-out signals assigned to these items of data.
It is conceivable to establish the zero transitions of the signals with the aid of a comparator whose inputs are fed with the signals as push-pull signals in inverted form and in non-inverted form. A comparator of this type emits from its output, for example, rectangular signals which change in binary value whenever the signals overshoot or undershoot the zero line. A comparator of this kind has the disadvantage, however, that the binary signals are emitted even when the signals are smaller than a given threshold value, or when the signals are disturbed in such a fashion that they contain dips which overshoot or undershoot the zero line.
It is also conceivable to provide an amplitude evaluator and to release the data pulses only when the amplitude of the signal is greater than a given threshold voltage prior to the zero transition. In this case, however, data pulses are also emitted when, due to dips, the signals temporarily overshoot or undershoot the zero line and the signal level was previously greater than the required threshold voltage.